These procedures provide a platform and compiler independent interface
for memory allocation. Programs that need to transfer ownership of
memory blocks between Tcl and other modules should use these routines
rather than the native malloc() and free() routines
provided by the C run-time library.

Tcl_Alloc returns a pointer to a block of at least size
bytes suitably aligned for any use.

Tcl_Free makes the space referred to by ptr available for
further allocation.

Tcl_Realloc changes the size of the block pointed to by
ptr to size bytes and returns a pointer to the new block.
The contents will be unchanged up to the lesser of the new and old
sizes. The returned location may be different from ptr. If
ptr is NULL, this is equivalent to calling Tcl_Alloc with
just the size argument.

Tcl_AttemptAlloc and Tcl_AttemptRealloc are identical in
function to Tcl_Alloc and Tcl_Realloc, except that
Tcl_AttemptAlloc and Tcl_AttemptRealloc will not cause the Tcl
interpreter to panic if the memory allocation fails. If the
allocation fails, these functions will return NULL. Note that on some
platforms, but not all, attempting to allocate a zero-sized block of
memory will also cause these functions to return NULL.

The procedures ckalloc, ckfree, ckrealloc,
attemptckalloc, and attemptckrealloc are implemented
as macros. Normally, they are synonyms for the corresponding
procedures documented on this page. When Tcl and all modules
calling Tcl are compiled with TCL_MEM_DEBUG defined, however,
these macros are redefined to be special debugging versions
of these procedures. To support Tcls memory debugging within a
module, use the macros rather than direct calls to Tcl_Alloc, etc.